直接在应用程序中呈现下载文件的预览

Question

我的应用程序有文件下载选项，它使用 alamofire 下载方法下载文件。下载完成后，我需要在不将文件保存到 internal/cloud 存储的情况下显示文件的预览。我怎样才能实现这个类似whatsapp的功能，在下载文件后显示预览。

func downloadFile(fileUrl: URL) {
    let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)

    Alamofire.download(fileUrl, to: destination)
        .response(completionHandler: { (downloadResponse) in
            self.dic.url = downloadResponse.destinationURL
            self.dic.uti = downloadResponse.destinationURL!.uti
            let rect = CGRect(x: 0, y: 0, width: 100, height: 100)
            self.dic.presentOpenInMenu(from: rect, in: self.view, animated: true)
        })
}

Answer 1

要显示文件预览，请使用 Apple 的 QuickLook 框架，该框架可让您嵌入大量文件类型的预览，包括 iWork 文档、Microsoft Office 文档、PDF、图像等，所有这些都无需写了很多代码。

首先，导入 QuickLook 框架，然后使您的视图控制器符合 QLPreviewControllerDataSource 协议。

参考：

代码：

class ViewController: UIViewController {
    var previewItem = URL!

    func downloadFile(fileUrl: URL) {
        let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)

        Alamofire.download(fileUrl, to: destination)
        .response(completionHandler: { (downloadResponse) in

            let previewController = QLPreviewController()
            previewController.dataSource = self
            self.previewItem = downloadResponse.destinationURL
            self.present(previewController, animated: true, completion: nil)
        })
    }
}

extension ViewController: QLPreviewControllerDataSource {
    func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
        return 1
    }

    func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {
       return self.previewItem as QLPreviewItem
    }
}

Answer 2

这是一个使用 Alamofire 的解决方案。有人可能会帮忙。

步骤：

Alamofire 有优秀的员工直接下载，也save/write 你的文件存入光盘。
Return下载文件的保存路径
使用UIDocumentInteractionController传递文件路径

然后呈现这个观点

 import Alamofire

     extension UIViewController : UIDocumentInteractionControllerDelegate{


     func downloadFileForPreview(fileName: String, fileExtension: String, filePath: String )  {


         let destination: DownloadRequest.DownloadFileDestination = { _, _ in
             let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]

             let fileWithExtension = "file.\(fileExtension)"

             let fileURL = documentsURL.appendingPathComponent(fileWithExtension)

             return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
         }
         //UtilitySwift.showUniversalLoadingView(true)
         Alamofire.download(filePath, to: destination).response {  response in
             debugPrint(response)
         //UtilitySwift.showUniversalLoadingView(false)

             if response.error == nil, let storeFilePath = response.destinationURL?.path {
                 //let image = UIImage(contentsOfFile: imagePath)
                 self.previewDocument(withFilePath: response.destinationURL)
                 print(storeFilePath)

             }

             else{
                 UtilitySwift.showErrorMessage(message: response.error?.localizedDescription ?? "Error occured when downloading" )
                 print(response.error?.localizedDescription ?? "")
             }

         }
     }


     //  Converted to Swift 5.1 by Swiftify v5.1.29672 - https://objectivec2swift.com/
     func previewDocument(withFilePath filePath: URL?) {

         var documentInteractionController: UIDocumentInteractionController?

         if filePath != nil {
             // Initialize Document Interaction Controller
             if let filePath = filePath {
                 documentInteractionController = UIDocumentInteractionController(url: filePath)
             }

             // Configure Document Interaction Controller
             documentInteractionController?.delegate = self as UIDocumentInteractionControllerDelegate

             //if not possible to open
             if !documentInteractionController!.presentPreview(animated: true) {
                 documentInteractionController?.presentOptionsMenu(from: CGRect.zero, in: self.view, animated: true)
             }

         } else {
             // error
             print("file preview error")
         }
     }
     //UIDocumentInteractionControllerDelegate
     public func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
         self
     }

     }

来自任何 UIViewController

的呼叫

self.downloadFileForPreview(fileName: "file", fileExtension: fileExt ?? "", filePath: REPLACE_WITH_DOWNLOAD_URL)

直接在应用程序中呈现下载文件的预览

Present preview of downloaded file directly in app

quicklook

ios

document-preview

swift